4(-1).+1

Решим пример:

$$\begin{aligned}
\left(6\frac{7}{20} - 15\frac{2}{5} : 4\frac{1}{2}\right) \cdot \frac{1}{10} + \frac{7}{20} = \left(\frac{127}{20} - \frac{77}{5} : \frac{9}{2}\right) \cdot \frac{1}{10} + \frac{7}{20} = \left(\frac{127}{20} - \frac{77}{5} \cdot \frac{2}{9}\right) \cdot \frac{1}{10} + \frac{7}{20} = \left(\frac{127}{20} - \frac{154}{45}\right) \cdot \frac{1}{10} + \frac{7}{20} = \left(\frac{127 \cdot 9 - 154 \cdot 4}{180}\right) \cdot \frac{1}{10} + \frac{7}{20} = \left(\frac{1143 - 616}{180}\right) \cdot \frac{1}{10} + \frac{7}{20} = \frac{527}{180} \cdot \frac{1}{10} + \frac{7}{20} = \frac{527}{1800} + \frac{630}{1800} = \frac{1157}{1800}
\end{aligned}$$

Ответ:$$\frac{1157}{1800}$$